This invention relates to a check valve for a tap for a gas or a liquefied gas cylinder and especially a check valve of this kind which has fever parts, which can be more economically produced and can also be more easily assembled, and which provides advantages in use.
The prior art check valve for a tap for a gas cylinder is a multipart structure comprising a cylindrical sleeve open at both ends, a first or primary seal ring carried by a separate seal support member threaded to the valve housing, a second annular seal disposed in a groove formed in the outer surface of the sleeve, and a third annular seal disposed within the annular sleeve and having a contact surface adapted to be gas tightly engaged by an actuator nipple of a gas pressure reducer when forcing the sleeve member against the force of a check valve closing spring into open position. This known check valve in view of its several parts cannot be economically manufactured and assembled and, moreover, both the first and the second seals are always exposed to the high pressure in the gas cylinder when the cylinder tap is open. Therefore, a check valve for a tap of a gas cylinder is desired, which has advantages in the above respects.
The object of the invention is to provide an improved check valve for a gas cylinder tap.
Another object of the invention is to provide an improved check valve for a gas cylinder tap which has fewer parts and can be economically produced and assembled.
A further object of the invention is to provide a check valve for a gas cylinder tap, wherein in the closed position of the check valve only the primary seal is exposed to the gas cylinder pressure.
To achieve this object there is provided in accordance with the invention a check valve for a tap of a gas or a liquefied gas cylinder including a housing having a bore therein having an inner circumferential surface, said bore having an axis and a mouth opening in a housing end surface; a valve body member axially movable in the housing bore between a check valve open and a check valve closed position and having a proximal annular portion defining a proximal annular end surface facing the housing bore mouth opening and a distal portion remote from said mouth opening, and said valve body member having gas flow passageway means therein opening out through said proximal portion of said valve body member and being in fluid communication, through the outer circumferential surface of the valve body member, with an annular interfacial gap defined between the outer circumferential surface of the valve body member and the inner circumferential surface of the housing bore; axially spaced primary and secondary seal means on the valve body member, said primary seal means being adapted to sealingly engage an associated generally axially extending primary sealing surface portion on the housing bore inner surface surrounding the valve body member, and said secondary seal means being adapted to sealingly engage at least one associated secondary sealing surface portion on said housing bore inner surface surrounding the valve body member, the primary seal means being on the outer circumferential surface of the valve body member distally of where the gas flow passageway means communicates with said annular interfacial gap, and the secondary seal means being on the valve body member proximally of where the gas flow passageway means communicates with said interfacial gap; spring means urging the valve body member in a proximal direction to the check valve closed position in which the primary seal means is in gas tight engagement with its associated axially extending primary sealing surface portion to prevent gas flow between the gas flow passageway means and a distal plenum chamber delimited between said housing bore and the valve body member, the valve body member being movable in an opposite, distal direction to said check valve open position wherein the primary seal means is distally disengaged from its associated primary sealing surface portion to permit gas flow between the plenum chamber and the gas flow passageway means through said annular interfacial gap; said valve body member having an annular contact surface extending around the gas passageway means at the proximal portion of the valve body member and adapted to be gas tightly engaged by an annular gas ducting member of an actuator means urging the valve body member against the spring force in the opposite, distal direction towards the open position.
The check valve of the invention eliminates the need for a separate seal support member by arranging the check valve primary seal means on the outer circumferential surface of the distal portion of the check valve body member and providing on the inner circumferential surface of the housing bore an axially extending primary sealing surface portion which is gas tightly engaged by the primary seal means in the closed position of the check valve. With the primary seal means in engagement with the axially extending sealing surface portion the annular interfacial gap surrounding the valve body member is isolated in use from the gas cylinder pressure and accordingly the secondary seal means provided for preventing gas leakage from the annular interfacial gap around the exterior of the valve body member beyond the proximal end thereof and out of the housing bore is not exposed to the gas cylinder pressure.
In accordance with another feature of the invention, which can be used together with the improved primary seal means or independently therefrom, the prior art secondary seal means provided to prevent gas leakage around the actuator end portion or proximal portion of the valve body member as well as the sealing ring tightly engageable by the actuator nipple of the gas pressure reducer, are replaced by a one-part annular sealing ring provided at the proximal end of the valve body member. This one-part sealing ring comprises an enlarged mass of resilient sealing material which is deflectable radially outwardly when engaged by the pressure reducer actuator nipple to force it radially outwardly to achieve gas tight sealing contact with the secondary interior sealing surface portion of the housing bore. This reduces wear of the one-part secondary sealing ring since either no or only a light contact of the secondary seal ring with the secondary sealing surface portion of the housing bore is needed when the primary seal means is in the seal engaged position wherein the secondary seal means is not exposed to the gas cylinder pressure. When the valve body member is urged to the open position the secondary one-part sealing ring is urged outwardly into enhanced gas tight sealing contact with the housing bore inner surface to prevent leakage of gas from the annular interfacial gap beyond the proximal end of the valve body member to the annular space surrounding the actuator nipple of the gas pressure reducer in the housing bore and therefrom out of the bore mouth opening to the environment of the gas cylinder tap.
The axially extending primary sealing surface portion formed in the housing bore for the primary seal means preferably has inclined outwardly extending ramp surfaces at both ends thereof to facilitate insertion of the valve body member with the primary seal means thereon into the housing bore during assembly and movement of the primary seal means from the check valve open position to the check valve closed position without causing damage to the primary seal means.
In accordance with another preferred feature of the invention the primary and the secondary seal means are rubber seals bonded by vulcanization to the metallic main part of the valve body member, whereby the valve body member is in fact a single part structure and the check valve comprises only three parts, namely the unitary valve body member, the return spring urging the check valve into its closed position after disengagement of the gas pressure reducer actuator nipple from the check valve body member, and a split retaining ring for retaining the check valve body member in the housing bore.
In accordance with another aspect of the invention, there is provided a check valve for a tap of a gas or a liquefied gas cylinder including a housing having a bore therein having an inner circumferential surface, said bore having an axis and a mouth opening in a housing end surface; a valve body member axially movable in the housing bore between a check valve open and a check valve closed position and having a proximal annular portion defining a proximal annular end surface facing the housing bore mouth opening and a distal portion remote from the mouth opening; primary seal means supported on one of the valve body member and the housing and cooperating with a primary sealing surface provided on the other of the valve body member and the housing, said primary seal means being in gas tight engagement with the primary sealing surface in the check valve closed position of the valve body member to thereby prevent gas flow between a gas flow passageway means formed in the interior of the valve body member and a distal plenum chamber delimited between said housing bore and the valve body member, and said primary seal means being disengaged from the primary sealing surface in the check valve open position of the valve body member to place the plenum chamber in fluid communication with the gas flow passageway means of the valve body member; spring means urging the valve body member in a proximal direction to the check valve closed position in which the primary seal means is in gas tight engagement with the primary sealing surface, the valve body member being movable against the spring force in an opposite, distal direction towards the check valve open position; and the valve body member having a secondary seal means comprising a secondary annular sealing element arranged at the proximal portion of the valve body member and having a proximally facing annular end surface defining the proximal end surface of the valve body member, said secondary sealing element having at least one annular sealing surface adapted to gas tightly engage a first secondary sealing surface portion on the housing bore inner surface, and said secondary sealing element being provided with an annular contact surface extending around the gas passageway means at the proximal portion of the valve body member and adapted to be gas tightly engaged by an annular gas ducting member of an actuator means urging the valve body member against the spring force in the opposite distal direction towards the open position.
In one embodiment the spring means surrounds the valve body member and engages a shoulder of the valve body member intermediate the opposite ends thereof and another shoulder in the housing bore between the primary and secondary sealing surface portions of different diameters in the housing bore. In another embodiment the spring means is between the distal end face of the valve body member and a bottom surface of the housing bore. In this embodiment the primary and secondary sealing surface portions in the housing bore may be of the same diameter and formed by a single continuous constant diameter surface portion of the circumferential surface of the housing bore.
In a further modified embodiment the secondary seal means is formed by a layer or coating of sealing material applied to the distal end portion of the valve body member. This coating of sealing material has in addition to the annular contact surface and the radially outwardly facing sealing surface for gas tightly engaging the secondary sealing surface portion of the housing bore inner surface, an additional distally facing sealing surface portion for gas tightly engaging an associated proximally facing sealing surface of the housing bore when the valve body member is in the check valve open position.